1. Field of the Invention
The present invention relates to the identification or authentication of a user of an electronic device by biometric data relative to him. The present invention more specifically relates to portable devices (for example, a smart card or an electronic key) exploiting a biometric identification of a user to allow or not access to any function (for example, the starting of a vehicle, the opening of a port, etc.).
2. Discussion of the Related Art
The biometric data used essentially include the recognition of an iris, a face or a fingerprint. This last application is the most current due to its easy exploitation on portable devices of key ring type or the like.
FIG. 1 very schematically shows, in the form of a block diagram, a conventional example of an architecture of a system of identification by fingerprint recognition.
Such a system essentially includes a sensor 1 of a fingerprint of a finger d laid on a sensitive surface of this sensor. The sensor takes an image of the papillary arrangement of the finger, digitizes it and processes it, to obtain a map of minutiae. The minutiae represent characteristic points of the papillary arrangement enabling considering two fingerprints as identical (generally, it is considered that there is a matching between two fingerprints when the number of identical minutiae in the two papillary arrangements is included between 8 and 17).
The mapping of the minutiae of the current fingerprint is stored (generally, temporarily) in a memory 2, assigned to the current image. This current image is compared by an adapted algorithm (block 3, MATCH) with reference minutia mappings forming templates stored in a database 4 or the like. In the specific application of the present invention to localized or portable identification devices, the reference database is reduced since a small number of users (generally, less than 10) need identification. The algorithmic comparison function 3 provides a result indicative of an authentication or no authentication of the user having laid his finger on the sensor.
A problem which arises in systems of identification by biometric data is linked to the storage of the reference templates. In particular, knowing a reference print stored in database 4, a possible pirate is then able to use the reference print to provide a file adapted to the current image storage block 2 or to comparator 3 to force a proper identification.
The most frequent piracies or “attacks” are the retrieval of the fingerprint as it is captured (at the output of sensor 1) or the copying of the content of a reference print stored in base 4.
It has already been provided to store the print templates in a coded or encrypted manner to make piracy more difficult. This type of coding is used for remotely stored print templates (for example, on a database accessible over a public network of Internet type). However, such a coding provide no satisfactory result and is further very poorly adapted to local authentication. In particular, it is enough for a pirate to know the content of a file, be it encrypted or not, to provide this file to the authentication comparator.
Document WO-A-0042577 describes a method and a device for a secure transmission of biometric authentication data over an Internet-type network. According to this document, a specific identifier is associated to a camera forming an iris image sensor. This identifier specific to the camera is used to scramble the digital biometric data image before its transmission over the network to a distant server. The comparison of the eye prints for authentication is here performed remotely from the sensor, the authentication server having the means necessary to decrypt the image, to compare it to uncrypted templates. A pirate can still deceive the system if he has managed to obtain a copy of a template.
Another problem of systems of identification by biometric data is due to the non-replaceable character (the data are generally said to be non-revocable) of the biometric data (as opposed to a confidential digital code). Accordingly, each time a print has been retrieved by a pirate from a database, the print holder can no longer use it. Since the number of fingers or eyes is limited, the biometric data that can replace a pirated print is limited.